From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 97E9DCD8C85 for ; Tue, 9 Jun 2026 06:22:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:References:Content-Type: Content-Transfer-Encoding:In-Reply-To:From:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=QNLMOTRHBXi4Z84O461LhX+rEh9cZpG943Cj00l7pcg=; b=u3KBvz2YlprdeBMhskb1r6c5V6 aJ753E2WLSAYCrjU1tjmY2qkXBkjDSmfD4Hc3e/NKKX/64SLSVEL1gR2OK0VWA7aQHf7QXgYjzR1q wvqH8gMYckSWWmTBjqMowU0GBXm1mEYLJFQ7u7BqgVwmoptcgLApzg4axKijiIjAZGHoNf9TaMG57 3qPSScuq2xxFSMGXZhhS6dnbBsR2xltJoKWW4hJuc5pUIGiCj5Q7pY4/NMOVVnPTe/tBM5xCpDNn1 1zW2x1foOTGmSwqiwvWR6/cv98TT6cOvgVkdYfSTJrEAWS+P0exqoD6UPxUbGDegS7pWsqy5y5MGX bbAgwQ9g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wWprH-00000004qfV-22NR; Tue, 09 Jun 2026 06:22:43 +0000 Received: from mailout1.w1.samsung.com ([210.118.77.11]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wWprA-00000004qeI-0qgD for linux-arm-kernel@lists.infradead.org; Tue, 09 Jun 2026 06:22:41 +0000 Received: from eucas1p2.samsung.com (unknown [182.198.249.207]) by mailout1.w1.samsung.com (KnoxPortal) with ESMTP id 20260609062228euoutp01a013ff920146714d1e396319eb6d1426~3VXdYuVGe1106711067euoutp01l for ; Tue, 9 Jun 2026 06:22:28 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 mailout1.w1.samsung.com 20260609062228euoutp01a013ff920146714d1e396319eb6d1426~3VXdYuVGe1106711067euoutp01l DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=samsung.com; s=mail20170921; t=1780986148; bh=QNLMOTRHBXi4Z84O461LhX+rEh9cZpG943Cj00l7pcg=; h=Date:Subject:To:Cc:From:In-Reply-To:References:From; b=kEkid4Lc9CpRO/3yyOzVz5QUMceUdCkVZHKebqPeaNlT6tnzDo5I4F3ZPZBXOk8On 5gBBhxvU8QM/nU5ODXUfDdfNgxHBxvxHcEGaliaAtVjJolwf72MxHzOQWCQV2TKj7I EB7BWOaYJ7qI4rHEe7WKsSSL3IF4YpJayVXGNTyo= Received: from eusmtip2.samsung.com (unknown [203.254.199.222]) by eucas1p2.samsung.com (KnoxPortal) with ESMTPA id 20260609062228eucas1p211850bcf6ea79ef270bc6fbe29ffafdb~3VXdClAs70378003780eucas1p2G; Tue, 9 Jun 2026 06:22:28 +0000 (GMT) Received: from [106.210.134.192] (unknown [106.210.134.192]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20260609062227eusmtip2cece3df82958ee4950f41c056ec8da55~3VXb-fGd70969909699eusmtip2E; Tue, 9 Jun 2026 06:22:27 +0000 (GMT) Message-ID: Date: Tue, 9 Jun 2026 08:22:26 +0200 MIME-Version: 1.0 User-Agent: Betterbird (Windows) Subject: Re: [PATCH v7 15/15] arm64: mm: Unmap kernel data/bss entirely from the linear map To: Ard Biesheuvel , linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, will@kernel.org, catalin.marinas@arm.com, mark.rutland@arm.com, Ard Biesheuvel , Ryan Roberts , Anshuman Khandual , Kevin Brodsky , Liz Prucka , Seth Jenkins , Kees Cook , Mike Rapoport , David Hildenbrand , Andrew Morton , Jann Horn , linux-mm@kvack.org, linux-hardening@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-sh@vger.kernel.org Content-Language: en-US From: Marek Szyprowski In-Reply-To: <20260529150150.1670604-32-ardb+git@google.com> Content-Transfer-Encoding: 8bit X-CMS-MailID: 20260609062228eucas1p211850bcf6ea79ef270bc6fbe29ffafdb X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-RootMTR: 20260609062228eucas1p211850bcf6ea79ef270bc6fbe29ffafdb X-EPHeader: CA X-CMS-RootMailID: 20260609062228eucas1p211850bcf6ea79ef270bc6fbe29ffafdb References: <20260529150150.1670604-17-ardb+git@google.com> <20260529150150.1670604-32-ardb+git@google.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260608_232238_457483_9F35CC42 X-CRM114-Status: GOOD ( 31.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Dear All, On 29.05.2026 17:02, Ard Biesheuvel wrote: > From: Ard Biesheuvel > > The linear aliases of the kernel text and rodata are also mapped > read-only in the linear map. Given that the contents of these regions > are mostly identical to the version in the loadable image, mapping them > read-only and leaving their contents visible is a reasonable hardening > measure. > > Data and bss, however, are now also mapped read-only but the contents of > these regions are more likely to contain data that we'd rather not leak. > So let's unmap these entirely in the linear map when the kernel is > running normally. > > When going into hibernation or waking up from it, these regions need to > be mapped, so map the region initially, and toggle the valid bit so > map/unmap the region as needed. > > Doing so is required because pages covering the kernel image are marked > as PageReserved, and therefore disregarded for snapshotting by the > hibernate logic unless they are mapped. > > Signed-off-by: Ard Biesheuvel This commit landed in yesterday's linux-next as commit 63e0b6a5b693 ("arm64: mm: Unmap kernel data/bss entirely from the linear map"). In my tests I found that it breaks booting of RaspberryPi3 and RaspberryPi4 boards with the following kernel panic: kvm [1]: nv: 570 coarse grained trap handlers kvm [1]: nv: 710 fine grained trap handlers kvm [1]: IPA Size Limit: 40 bits Unable to handle kernel paging request at virtual address ffff000003a23000 Mem abort info:   ESR = 0x0000000096000147   EC = 0x25: DABT (current EL), IL = 32 bits   SET = 0, FnV = 0   EA = 0, S1PTW = 0   FSC = 0x07: level 3 translation fault Data abort info:   ISV = 0, ISS = 0x00000147, ISS2 = 0x00000000   CM = 1, WnR = 1, TnD = 0, TagAccess = 0   GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0 swapper pgtable: 4k pages, 48-bit VAs, pgdp=0000000002609000 [ffff000003a23000] pgd=0000000000000000, p4d=180000003b3ff403, pud=180000003b3fe403, pmd=180000003b3e6403, pte=00e8000003a23f06 Internal error: Oops: 0000000096000147 [#1]  SMP Modules linked in: CPU: 3 UID: 0 PID: 1 Comm: swapper/0 Not tainted 7.1.0-rc1+ #16768 PREEMPT Hardware name: Raspberry Pi 3 Model B (DT) pstate: 80000005 (Nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) pc : dcache_clean_inval_poc+0x24/0x48 lr : kvm_arm_init+0xa8c/0x165c sp : ffff8000844bbd00 ... Call trace:  dcache_clean_inval_poc+0x24/0x48 (P)  do_one_initcall+0x68/0x4f4  kernel_init_freeable+0x24c/0x360  kernel_init+0x24/0x1dc  ret_from_fork+0x10/0x20 Code: 9ac32042 d1000443 8a230000 d503201f (d50b7e20) ---[ end trace 0000000000000000 ]--- Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b SMP: stopping secondary CPUs Kernel Offset: disabled CPU features: 0x00000000,03000008,00040000,0400421b Memory Limit: none ---[ end Kernel panic - not syncing: Attempted to kill init! exitcode=0x0000000b ]--- > --- > arch/arm64/mm/mmu.c | 45 ++++++++++++++++++-- > 1 file changed, 41 insertions(+), 4 deletions(-) > > diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c > index 7b18dc2f1721..07a6fa210171 100644 > --- a/arch/arm64/mm/mmu.c > +++ b/arch/arm64/mm/mmu.c > @@ -24,6 +24,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -1056,6 +1057,29 @@ static void __init __map_memblock(phys_addr_t start, phys_addr_t end, > end - start, prot, early_pgtable_alloc, flags); > } > > +static void mark_linear_data_alias_valid(bool valid) > +{ > + set_memory_valid((unsigned long)lm_alias(__init_end), > + (unsigned long)(__bss_stop - __init_end) / PAGE_SIZE, > + valid); > +} > + > +static int arm64_hibernate_pm_notify(struct notifier_block *nb, > + unsigned long mode, void *unused) > +{ > + switch (mode) { > + default: > + break; > + case PM_POST_HIBERNATION: > + mark_linear_data_alias_valid(false); > + break; > + case PM_HIBERNATION_PREPARE: > + mark_linear_data_alias_valid(true); > + break; > + } > + return 0; > +} > + > void __init mark_linear_text_alias_ro(void) > { > /* > @@ -1064,6 +1088,21 @@ void __init mark_linear_text_alias_ro(void) > update_mapping_prot(__pa_symbol(_text), (unsigned long)lm_alias(_text), > (unsigned long)__init_begin - (unsigned long)_text, > PAGE_KERNEL_RO); > + > + /* > + * Register a PM notifier to remap the linear alias of data/bss as > + * valid read-only before hibernation. This is needed because the > + * snapshot logic disregards PageReserved pages (such as the ones > + * covering the kernel image) unless they are mapped in the linear > + * map. > + */ > + if (IS_ENABLED(CONFIG_HIBERNATION)) { > + static struct notifier_block nb = { > + .notifier_call = arm64_hibernate_pm_notify > + }; > + > + register_pm_notifier(&nb); > + } > } > > #ifdef CONFIG_KFENCE > @@ -1193,10 +1232,8 @@ static void __init map_mem(void) > flags); > } > > - /* Map the kernel data/bss read-only in the linear map */ > - __map_memblock(init_end, kernel_end, PAGE_KERNEL_RO, flags); > - flush_tlb_kernel_range((unsigned long)lm_alias(__init_end), > - (unsigned long)lm_alias(__bss_stop)); > + /* Map the kernel data/bss as invalid in the linear map */ > + mark_linear_data_alias_valid(false); > } > > void mark_rodata_ro(void) Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland